This invention relates generally to energy storage devices, and more particularly, to an apparatus and method for selectively interconnecting a number of independent energy storage cells disposed in a sealed housing.
The demand for new and improved electronic and electromechanical systems has placed increased pressure on the manufacturers of energy storage devices to develop battery technologies that provide for high energy generation in a low-volume package. Conventional battery systems, such as those that utilize lead acid for example, are often unsuitable for use in high-power, low-weight applications. Other known battery technologies may be considered too unstable or hazardous for use in consumer product applications.
A number of advanced battery technologies have recently been developed, such as metal hydride (e.g., Ni-MH), lithium-ion, and lithium polymer cell technologies, which would appear to provide the requisite level of energy production and safety margins for many commercial and consumer applications. Such advanced battery technologies, however, often exhibit characteristics that provide challenges for the manufacturers of advanced energy storage devices.
In accordance with a conventional advanced battery design, individual cells are hardwired together and to the positive and negative power terminals of the battery. Various electronic components which may be incorporated into the battery design must also be hardwired to the cells. It can be appreciated that such conventional interconnection approaches provide for little, if any, flexibility when attempting to alter the series and/or parallel hardwired connections between the cells and components.
Moreover, the wiring process typically employed in the fabrication of conventional advanced batteries is generally complicated and time consuming. An assembly defect of particular concern to the manufacturers of conventional advanced batteries involves unintentional wiring shorts which develop during the wiring process. Such manufacturing defects typically result in a reduction in the performance and service life of the battery, and often represent a significant safety concern.
Other characteristics of advanced battery technologies provide additional challenges for the designers of advanced energy storage devices. For example, certain advanced cell structures are subject to cyclical changes in volume as a consequence of variations in the state of charge of the cell. The total volume of such a cell may vary as much as five to six percent during charge and discharge cycling. Such repetitive changes in the physical size of a cell significantly complicates the mechanical housing design, and electrical connection strategy. The electrochemical, thermal, and mechanical characteristics of an advanced battery cell must typically be well understood and appropriately considered when designing an energy storage system suitable for use in commercial and consumer devices and systems.
There is a need in the advanced battery manufacturing industry for an energy storage device that exhibits high-energy output, and one that provides for safe and reliable use in a wide range of applications. There exists a further need for an effective interconnection strategy which provides flexibility and reliability when interconnecting a number of independent energy storage cells contained within a sealed housing to meet specified current and voltage ratings. The present invention fulfills these and other needs.
The present invention is directed to an improved electrochemical energy storage device. The electrochemical energy storage device includes a number of solid-state, thin-film electrochemical cells which are selectively interconnected in series or parallel through use of an integrated interconnect board. The interconnect board is typically disposed within a sealed housing or shell which also houses the electrochemical cells, and includes a first contact and a second contact respectively coupled to first and second power terminals of the energy storage device. The interconnect board advantageously provides for selective series or parallel connectivity with the electrochemical cells, irrespective of cell position relative to one another within the housing. In one embodiment, a sheet of conductive material is processed by employing a known milling, stamping, or chemical etching technique to include a connection pattern which provides for flexible and selective interconnecting of individual electrochemical cells within the housing, which may be a hermetically sealed housing. The voltage and current characteristics of the energy storage device are alterable by altering the configuration of the connection pattern. Fuses and various electrical and electro-mechanical devices, such as bypass, equalization, and communication devices for example, may also be mounted to the interconnect board and selectively connected to the electrochemical cells.